JPH05252491A - Multi-page teletext decoder - Google Patents

Abstract

PURPOSE: To collect and store teletext pages as quickly as possible and to refresh them frequently by constituting a control circuit so that a request number appearing after a skipped page number is selected. CONSTITUTION: A received composite video signal CVBS is supplied to a data slicer 21, which is supplied with a TTD signal from a television line and supplies the signal to a DVT circuit 22. The DVT circuit 22 is equipped with eight gathering circuits to automatically gather supplied teletext pages with request numbers by the gathering circuit and store the pages in selected segments of a page memory 23 and is also equipped with a display circuit to output an RGB signal and an FBL signal. The gathering circuits supply interrupt signals IRQ to the control circuit 24 when request pages are received in relation with a gathering register 221 and a point register 222. A memory M25 is coupled with a communication bus and store request page numbers.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a multi-page teletext decoder which collects and stores a plurality of teletext pages. The invention also relates to a television signal receiver provided with such a multi-page teletext decoder. Such a receiver can be, for example, a television set or a video recorder.

[0002]

2. Description of the Related Art A multi-page teletext decoder of the type described above is called "IEEE Transactions on Consume".
r Electrics, Vol. 37, No. 3 ", August 1991,
pp. 441-448 "The New Mul"
tipage Teletext Decoders ". As described in chapters 6 and 7 of this paper, this teletext decoder has a page memory for storing teletext pages, and a teletext with a supplied request number. It comprises at least one collecting circuit for collecting and accumulating pages, means for fixing the request numbers of a plurality of pages to be collected, and a control circuit for supplying the request numbers to the collecting circuit.

The request number constitutes the page number of the teletext page to be collected and stored. The accumulated pages can be referenced by the user without waiting time. The request number is programmed by the user and stored in the page number memory, for example. The request number can also be determined by the transmitter.
The transmitter sends the number of the page most likely to be selected as the next few pages for each page. The method of determining and fixing the request number is not relevant to the present invention.

As described in the above-mentioned paper, when a teletext page is received and stored, the control circuit provides a new request number to the collection circuit. In this way, all requested pages are sequentially collected and stored. The entire accumulation procedure is repeated each time to refresh the accumulated page.

[0005]

Teletext pages are sent in a repeating cycle. Theoretically, all requested pages could be collected and stored within that one cycle. However, in practice, it takes some time to select the next request number and supply it to the collecting circuit. In particular, the control circuit is coupled to the acquisition circuit via a relatively slow serial bus. Therefore, there is some time lapse between the receipt of the page and the actual start of the collection of the next requested page. This "dead time" has a length such that the next page to be collected has passed. In this case, the entire cycle will pass before collecting the requested pages. In this case, the storage of all requested pages can continue for many cycles. However, as a result, it takes a long time to obtain the entire page for immediate display. Further, since the accumulated pages are not refreshed frequently, it is possible that the pages will contain stale data information when displayed.

Generally, teletext pages are transmitted in ascending numerical order using ascending page numbers. It is not uncommon to group pages and create page number "gaps" between groups. For example, a group of domestic news pages has page numbers 103 to 109.
, And the next group of foreign news pages includes page numbers 112-118. The above problem is that two teletext pages with consecutive page numbers (eg 10
3 and 104) need to be stored, but also when the two pages to be collected are on either side of the "void" (eg 107 and 112).

The order of page numbers may be regularly interrupted by "interrupted order" pages. These pages are pages having page numbers that do not match in numerical order. For example, it is common practice to send frequently used pages several times per cycle. Such a page is not only sent at the correct position in numerical order within the send cycle, but also at other positions within this cycle.
Therefore, the problems described above can also occur when the numbers of the two pages to be collected are far apart, but appear consecutively with each other within the transmission cycle.

It is an object of the present invention to provide a multi-page teletext decoder which rapidly stores the required teletext pages and refreshes them frequently.

[0009]

To this end, the present invention provides a page memory for storing teletext pages.
It comprises at least one collecting circuit for collecting and storing teletext pages having a supplied request number, a means for fixing the request numbers of a plurality of pages to be collected, and a control circuit for supplying the request numbers to the collecting circuit. In the multi-page teletext decoder, the control circuit skips a predetermined number of page numbers after the number of the received page in a predetermined cyclic page number sequence, and among the plurality of request numbers,
It is characterized in that the request number that appears first after the skipped page number in this cyclic page number sequence is selected. With this arrangement, pages that come immediately after or almost immediately after the received page, and therefore pages that cannot be collected in the same cycle, are prevented from being fed to the collection circuit.

The predetermined cyclic page number sequence preferably comprises the page numbers of the teletext pages actually transmitted within the transmission page sequence. However, in reality, teletext pages are sent in a regular number order using ascending page numbers. In World System Teletext, the most common teletext system, these page numbers are 100-899 page numbers. The cyclic page number sequence can be composed of all transmittable page numbers in ascending order. The number of skip pages in this page number sequence can be determined experimentally depending on the "dead time" described above. If the dead time is 125 msec, up to 4 teletext pages will be sent within this time. In this case, four page numbers are skipped each time one page is received. Corresponding teletext pages can no longer be collected within the same cycle. From the request page numbers, select the request number that appears first after the skipped page number. This request number is most likely the next collectable teletext page request number. If the request number continues with a smaller limit, more pages can be collected within that cycle. In this way it is achieved that the teletext decoder stores and refreshes as many teletext pages as possible in one cycle.

In the preferred embodiment of the multi-page teletext decoder of the present invention, means are provided for marking the page number of the teletext page sent to the decoder. In this example, the cyclic page number series is composed of marked page numbers. This example is particularly useful because its operation is not affected by page number "gaps" that may occur in the transmit cycle. In this example, the cyclic page number sequence actually comprises only the page numbers of the pages that actually exist. Pages skipped in this page number sequence represent pages that were transmitted during "dead time" and cannot be collected in the same cycle. It is known per se from DE 3622308 and EP 0406972 to provide the teletext decoder with means for marking transmitted teletext pages. However, these known teletext decoders do not skip a certain number of marked numbers to determine the next collectable page.

In order to collect the skipped request numbers in subsequent cycles, another embodiment of the decoder of the present invention uses:
The control circuit is configured to store a storage indicator for each request number of stored pages and select a request number for which the storage indicator has not yet been stored. Once all requested pages have been collected and accumulated, the accumulation indicator can be cleared for refreshing.

In another embodiment of the decoder of the present invention, means for determining whether the page number of the received page is different from the order of the cyclic page number sequence and, if different, determining the page number of the next received page. To provide. In this case, the fastest next collectable page can be determined even when receiving an "interrupted order" page.

When the decoder is provided with a plurality of collecting circuits, the control circuit stores a request indicator for each request number supplied to these collecting circuits and selects a request number for which a request indicator has not yet been stored. To configure. With such a teletext decoder, it is avoided that two or more acquisition circuits simultaneously acquire one and the same page. Therefore, the desired teletext page can be collected as fast as possible.

The present invention will be described in detail with reference to the drawings.

[0016]

FIG. 1 shows the overall structure of a television receiver provided with a multi-page teletext decoder according to the present invention. The television transmission signal received by the antenna 10 is supplied to the tuner / demodulation circuit 11. The obtained composite video signal CVBS of the selected television program is supplied to the video signal processing circuit 12 and the multi-page teletext decoder 20. In the normal television operating condition of the receiver, the basic color signal R'G'B 'from the video signal processing circuit 12 is supplied to the display screen through the selector 13 so that the user can watch the received television program. In the teletext operation state that can be selected by the user, the basic color signals RGB from the teletext decoder 20 are displayed on the display screen 14 via the selector 13.
The selector 13 is driven by the blanking signal FBL generated in the teletext decoder. The operating instructions given by the user, in particular the teletext page number, are generally generated in the (remote) control unit 15 and supplied to the operating circuit 17 via the receiving circuit 16. The teletext decoder 20 is connected to this operating circuit via the command bus 18 and receives the page number of the desired teletext page. Further, the interface 19 is connected to the command bus 18 so that the operating circuit 17 can control the tuning of the television receiver, the brightness and the volume of the television receiver through the interface. This is indicated by appropriate symbols in the figure.

FIG. 2 shows the configuration of the teletext decoder 20. The received decoded video signal CVBS is supplied to the data slicer 21 including, for example, an integrated circuit SAA5191 manufactured by Philips. The data slicer 21 extracts a teletext data signal TTD from a television line having teletext information and supplies this signal to a digital video teletext (DVT) circuit 22 which is composed of, for example, an integrated circuit SAA9042 manufactured by Philips. The DVT circuit accommodates the collection, storage and display of multiple teletext pages. To this end, DV
The T circuit is a page memory 23, for example, 128 Kbytes DR
Connect to AM. This memory can be viewed as being divided into 64 segments of 2K bytes each suitable for storing teletext pages. The DVT circuit is further routed via the I ² C bus, for example the Philips type MAB808.
4 to a control circuit 24 consisting of a microprocessor.

The DVT circuit 22 comprises eight acquisition circuits,
Each collection circuit automatically collects the teletext page with the supplied request number and stores this page in the page memory 23.
Accumulate in the selected segment of. Each collection circuit is associated with a collection register 221 that stores the request number of the teletext page that the collection circuit should collect. These acquisition registers will be denoted hereafter by A (i) (i = 1, --- 8). In addition, each collection circuit is associated with a pointer register 222 that indicates on which segment of the page memory the requested page should be stored upon receipt. Hereinafter, these pointer registers are represented by P (i) (i = 1, --8). Register A
(I) and P (i) may access the control circuit 24 via the I ² C bus. The collection circuit also provides an interrupt signal IRQ to the control circuit 24 when the requested page is received and stored. Further, the DVT circuit 22 includes a display circuit for converting the stored page into an RGB signal capable of displaying and a blanking signal FBL.

The memory M (25) is coupled to the communication bus 18 and stores a plurality of requested page numbers.
In the following, it is assumed that the user programs the page numbers of the desired pages in the memory M. In practice, the memory M stores various page numbers for various TV transmitting stations. This memory is preferably a non-volatile memory, so that the stored request numbers are retained even after the television receiver is switched off.

The operation of the teletext decoder is controlled by the control circuit 2.
4 is performed based on the control program executed. In this example, the control program comprises a storage program that collects and stores the requested teletext pages, and a display program that displays the page instructed by the user.
The display program runs in the teletext operating mode. Since this is generally known, detailed description is omitted. The storage program is continuously executed in both the television operation mode and the teletext operation mode.

FIG. 3A shows a flowchart of a first example of the storage program. In this example, the multi-page teletext decoder comprises only one acquisition circuit. It is assumed that the requested page number corresponding to the selected transmitting station is stored in the memory location M (n) (n = 1 --- N) of the memory M. Furthermore, each memory location is associated with a storage indicator S (n),
This indicator has the logical value "0" to indicate that the corresponding teletext page has not yet been collected and stored.

The storage program starts after the user selects one transmitting station. In the initial step 30 of the storage program, the storage indicators S (1), --- S (N) are erased. In step 31, the index n is set to the initial value 1. In this step, the void register P is also set to the initial value 1. This means that the teletext pages collected by the collecting circuit are stored in the first segment of the page memory. In step 32, the request number stored in memory location M (n) is transferred to collection register A. At this time, the collecting circuit automatically collects the teletext page having the first request number and stores it in the page memory. In step 33, wait time is observed for the generation of an interrupt request signal indicating that this page has been received. If this page is not sent, the maximum wait time is observed. In step 34, the corresponding accumulation indicator S (n) is set to the logical value "1" to indicate that the teletext page has been accumulated.

At step 35, the current page number PAG
To decide. The current page number consists of the request number M (n) of the page just stored. Next, in step 36, the lower limit number is fixed. This lower bound number forms the lowest page number of the next page to be collected. This minimum page number is obtained by skipping a predetermined number of numbers in the cyclic sequence of teletext page numbers 100-899. In the present example this is achieved by adding a predetermined number C to the current page number PAG. Next, in step 37, the index n of the first request number following the minimum page number MP is searched in the memory M. Ignore the request number of the already stored page. Step 37 can be implemented in various ways. If the request numbers in memory M are arranged in ascending numerical order, this step may comprise a program loop to search for the next position n in memory M having a request number greater than the minimum page number MP. Such a program loop is expressed in pseudo programming language notation as, for example, do n = n + 1 until M (n) ≧ MP and S (n) = “0”. If the request numbers are not arranged in ascending order, this step is the request number M (i) (i = 1 ---
N) and the smallest difference between the smallest page number MP (DIF). Such a program can be expressed as for i = 1 to N do if M (i) -MP <DIF and S (i) = “0” then DIF = M (i) -MP: n = i. In any case, these program loops are held in the index n of the memory M, and the lower limit number MP
Then, the request number M (n) which is the first request number in the numerical order and whose storage indicator is still "0" is searched.

In step 38, all accumulation indicators S
(I) Check whether (i = 1 --- N) has the logical value "1". If no, the stored program is step 3
Return to 2, request number M just found here
(N) is supplied to the collecting circuit. In step 39, the pointer register P is incremented by 1 to store the requested page in the next segment of page memory. When it is confirmed in step 38 that all desired pages have been accumulated,
The accumulation program returns to the initial step 30. The full store program is then run again to refresh the already stored page.

It should be noted that, for complete understanding, teletext page numbers are in the range 100-899. When the arithmetic processing such as addition and comparison is as described above, the cyclic operation described above is performed within the above range. Therefore, 899 + 1 = 100.

The value of C is experimentally determined. The important point is that the receiver for a single page has a series of steps 34-39.
And the time required to execute 32. In particular, it searches for the next request number in memory M and sends this to a fairly slow I
Supplying the acquisition circuit via the ² C bus is a time consuming process in an actual teletext decoder. As a result of the experiment, it was found that about 4 teletext pages were passed during this time. The optimum value of the constant C in this case is C = 5. However, the use of larger values of C is also valid and at least avoids requesting pages that can no longer be collected in the same cycle.

The above description will be made on an actual example.
In this example, the multi-page teletext decoder is page 1
10-120 shall be collected and accumulated. The constant C is 5
Is. After receiving page 110, page 115 is requested. This page is received within the same cycle. The same is true for the next required page 120. In the second cycle, the decoder receives pages 111 and 116. The desired page is collected and accumulated in 5 cycles, as shown in the table below. On the other hand, when requesting a plurality of pages in the normal order 110, 111, 112, etc., 11 cycles are required to collect all the pages.

[Table 1]

In step 35 of the storage program described above, the current page number PAG consists of the page number of the page just received. This received page may also be an "interruption order" page. This is a page that is transmitted at any position in the cycle and its number is different from the order of numbers when it was received. With the addition of the constant C, the next request number will not be the next expected page, which is the earliest expected page.

FIG. 3B shows one possible example of a program step 35 that prevents this disadvantage. In this case, step 35 comprises substep 351 to check whether the received page is an "interrupted order" page. In practice, the "interrupted order" page is provided with the appropriate bit at the transmitting station, so sub-step 351 examines this bit. If the received page is an "interrupt page", then in substep 352 the "don't care" page number X
Supply XX to the acquisition circuit. In sub-step 353, the latency is observed for the reception of this arbitrary page. This is a very short waiting time. It is then checked if this arbitrary page is an "interrupted order" page. At the same time that a "normal" page is received, its page number is read in substep 354 and considered as the current page number PAG. It takes some extra time to request and receive a "don't care" page. Constant C
Is preferably temporarily adapted to this extra time.

FIG. 4 shows a flowchart of another example of the storage program executed by the control circuit. This example differs from the previous example in that the control circuit marks the page number of the teletext page actually transmitted by the transmitting station. Furthermore,
In this example, multiple collection circuits are used to collect and store the desired pages.

In step 40 of this accumulation program, all table positions T (i) of the transmission table T (i = 1
00, --- 899) is deleted. This transmission table T is shown in FIG. 5A. This table T is, for example, an 800-bit R which forms part of the microprocessor 24 (FIG. 2).
It is formed by AM. In this example, the logical value T (i) = "0" obtained by erasing means that the teletext page with the number i is not present in the transmitted signal. The eighth of the eight available collection circuits is for fixing the transmitted page number. For this purpose, in step 41 the "don't care" page number xxx is provided to the corresponding collection register A (8).

In addition to the accumulation indicator S (i) already explained,
The memory M comprises a request indicator Q (i) corresponding to each request number M (i) as shown in FIG. 5B. This indicates which of the seven available collection circuits will collect page M (i). Q (i) can take the values 0, --7. A value of 0 indicates that page M (i) is not collected, a value of 1, ---
7 corresponds to the number of the collecting circuit to which the request number M (i) is supplied.

In step 42, the total accumulated sign S
(I) is deleted to indicate that pages have not been accumulated yet. In addition, the total request indicator Q (i) is set to 0 to indicate that seven collection circuits have not yet collected the page. Next, in step 43, the request numbers M (1), --- M
(7) is supplied to the seven collecting circuits. Corresponding pointer registers P (1), --- P (7) each obtain a different initial value to store the seven requested pages in different segments of the page memory. Request indicator Q (1), --- Q
(7) receives the number from the corresponding collection circuit. In step 44, the constant Pf receives the number 8 of the next free sector.

In step 45, one of the eight acquisition circuits
Observe the latency as to which received the page.
In step 46, the page number of the received page is fixed and assigned to the variable PAG. At step 47, a logical "1" is written to the corresponding position T (PAG) in the transmission table, indicating that the teletext page with the number PAG is actually present in the transmission signal.

Next, in step 48, it is verified which acquisition circuit has acquired this page. The number of this collecting circuit is indicated by q in this example. If it is determined in step 48 that the page has been received by the eighth collection circuit, then a "don't care" page has been received and the store program returns to step 45 to wait for the next page. In this way, the numbers of all teletext pages present in the transmission signal are marked in the transmission table T with the value "1".

If it is determined in step 48 that the page has been received by one of the other seven collection circuits, then one of the requested pages has been received. This page is automatically stored in the segment of page memory allocated by the pointer register P (q). In step 49, the request number of the page just found is searched in the memory M. This step 49 is as follows, for example. n = 0: do n = n + 1 until Q (n) = q In step 50, the accumulation indicator S (n) is set to the logical value “1”.
To indicate that the corresponding page M (n) has been stored. In addition, the request indicator Q (n) is set to the value 0 to indicate that this page is no longer instantaneously collected.

In step 51, the page number of the next collectable page is determined. For this purpose, a predetermined number of mark positions are skipped from the table position of the current page number in the transmission table T. The mark position is a logical value "1" corresponding to the teletext page actually transmitted.
Means the table position with. Thus, the numbers of teletext pages that were not sent are automatically ignored. This differs from the previous example of adding the constant C to the current page number. Therefore, even if there is a "void" in the transmission page number, it is not affected. Step 51 can be written as follows in a pseudo programming language. for i = 1 to C dodo PAG = PAG + 1 until T (PAG) = “1” Here, the constant C represents the number of pages that cannot be collected during the predetermined time after receiving the page. At the start of this program loop, PAG represents the current page number. Next, the next mark table position is searched C times. When leaving the loop,
PAG is the number of the next collectable page (minimum page number M
(Also referred to as P).

In step 52, a request number equal to or greater than the minimum page is searched in memory M from memory location n where the current page number is stored. Assuming that the request numbers in memory M are arranged in numerical order, step 52 is as follows. do n = n + 1 until M (n) ≧ PAG and S (n) = “0” and
Q (n) = 0 In this step, pages already accumulated (accumulation indicator S (n) has a logical value “1”) or pages already collected by the other seven collecting circuits (request indicator Q ( n)
Is required to have a non-zero value).

In step 53, the found page number M (n) is supplied to the free collecting circuit q. Further, the number Pf of the free segment next to this page number is assigned to the corresponding pointer register P (q). Register the new page request with the request indicator Q (n). In step 54, the number Pf of the next free memory segment is incremented by 1. The accumulation program then returns to step 45 to observe the latency for the next receipt of the page. The flow chart of FIG. 4 does not show the program step for checking whether all pages have already been stored. These steps have been described in the previous example.

The above will be described below with reference to an actual example.
Teletext transmission is now on pages 103-107 and 1
Including page numbers 12 to 118, intermediate page numbers 108 to 111
Shall not exist. Further, 106, 113 and 1
It is assumed that 16 is the request number. One of these numbers
06 is fed to one of the acquisition circuits, pages 113 and 1
16 is not requested yet. The constant C is assumed to be 5. When page 106 is received, step 51 of the accumulation program indicates that page 115 is the next collectable page. In fact, according to the transmission table T, after page 106, pages 107, 112, 11
3,114,115 --- is sent and step 51 searches for its fifth page. Therefore, the first request number above this number is 116, and the collection of the requested page 113 is postponed.

On the other hand, in the previous example, 106 + C = 1
Page 113 is requested as the first request number greater than or equal to 11. However, page 113 cannot be collected within the same cycle. For this reason, in the previous example, it is preferable to consider the "void" of the transmitted page number when determining the constant C.

In the above, it is assumed that the teletext pages are transmitted in the ascending order of numbers. This is almost always the case. This sequence is interrupted by the "interrupt sequence" page that sometimes occurs. However, it is possible to realize a memory-type transmission table that stores the page numbers of all transmission pages in the transmission order. In this case, the request numbers are also arranged in the order of transmission. In this case, the determination of the next collectable page is independent of the transmission order within the cycle.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a television receiver provided with a multi-page teletext decoder of the present invention.

FIG. 2 is a configuration diagram of the multi-page teletext decoder shown in FIG.

FIG. 3 is a flowchart of an example of a control program executed by the control circuit shown in FIG.

4 is a flowchart of another example of a control program executed by the control circuit shown in FIG.

5 shows a possible example of a memory used in the teletext decoder of FIG.

[Explanation of symbols]

 10 Antenna 11 Tuner / Demodulator Circuit 12 Video Signal Processing Circuit 13 Selector 14 Display Screen 15 (Remote) Control Unit 16 Receiving Circuit 17 Operating Circuit 18 Bus 19 Interface 20 Teletext Decoder 21 Data Slicer 22 Digital Video Teletext (DVT) Circuit 23 Page memory 24 Control circuit 25 Memory 221 Collection register 222 Pointer register

Claims (5)

[Claims] 1. A page memory for storing teletext pages, at least one collecting circuit for collecting and storing teletext pages having a supplied request number, and means for fixing request numbers of a plurality of pages to be collected. , A multi-page teletext decoder comprising a control circuit for supplying a request number to a collection circuit, said control circuit comprising:
A request that skips a predetermined number of page numbers after the number of the received page in a given cyclic page number sequence and appears first in the plurality of request numbers after the skipped page number in this cyclic page number sequence. Teletext decoder characterized by being configured to select a number. 2. The teletext decoder according to claim 1, comprising means for marking the page number of a transmitted teletext page, the cyclic page number sequence being composed of marked page numbers. Teletext decoder. 3. The control circuit is configured to store an accumulation indicator for each request number of accumulated pages and select a request number for which an accumulation indicator is not yet stored. Alternatively, the teletext decoder described in 2. 4. The teletext decoder comprises means for determining whether the page number of the received page is different from the order of the cyclic page number sequence, and if not, determining the page number of the next received page. The teletext decoder according to any one of claims 1 to 3, wherein 5. The control circuit comprises a plurality of collecting circuits, wherein the control circuit stores a request indicator for each request number supplied to the collecting circuits, and selects a request number for which a request indicator is not yet stored. The teletext decoder according to claim 1, wherein the teletext decoder is configured.